First report of burst-pulse vocalizations from white-beaked dolphins (Lagenorhynchus albirostris)

Abstract

Dolphin vocalizations are generally categorized as tonal whistles or pulsed clicks. Pulsed signals in dolphins are usually associated with echolocation, however an increasing number of species are found to produce burst pulse signals which may be used for communication. Groups of white-beaked dolphins (Lagenorhynchus albirostris) were recorded from a 4.2 m rigid inflatable boat near Halifax, Canada with a hydrophone towed 25 m behind the boat at a depth of approximately 5m, and an M-Audio 24/96 digital recorder (16 bit, 96 kHz). During one 23-minute encounter, 11 burst pulse segments were recorded. Mean burst pulse duration was 0.83s (SD 0.51, range 0.22s - 1.74s). Seven segments with high signal to noise ratios were manually selected for analysis in Matlab. Mean pulse rate was 765 Hz (SD 182.2, range 552 Hz - 941 Hz). These durations and pulse rates are similar to those reported for other dolphin species. These vocalizations were made immediately before the group began actively swimming away from the boat at high speed, suggesting that these vocalizations are used in agonistic encounters as suggested for other species of dolphins. This is the first time burst-pulse vocalizations have been reported in this species.